The herbivore's dilemma: Trends in and factors associated with heterosexual relationship status and interest in romantic relationships among young adults in Japan-Analysis of national surveys, 1987-2015

Sexual Behaviors among Individuals Aged 20-49 in Japan: Initial Findings from a Quasi-Representative National Survey, 2022

Nationally representative data on sexual health and behaviors in Japan are scarce. We conducted an online survey, including questions about a range of topics related to sexual behaviors and outcomes. The sample, including 8000 men and women aged 20-49 years in Japan, was stratified by sex and weighted with respect to age, marital status, and region of residence to reflect the population of Japan. Of the women, 82.9% and 10.0% reported that they were heterosexual and asexual, respectively; corresponding proportions for men were 87.4% and 6.9%. 15.3% of women and 19.8% of men reported never having had any partners with whom they engaged in vaginal, anal, or oral sex. 45.3% of women and 44.5% of men reported not having had any sexual partners during the past year; this proportion was highest among women aged 40-49 years (51.7%) and men aged 20-29 years (55.1%). The proportion of those reporting satisfaction with their sex life was 27.8% for women and 23.1% for men; 17.6% of women and 27.1% of men reported dissatisfaction. Pornography use of ≥3 times per week was most common among those aged 20-29 years (6.5% of women; 34.8% of men), and the frequency of pornography use decreased slightly with age. 4.0% of women and 48.3% of men reported ever having used commercial sex worker services in their lifetime. This survey-based study provides data on sexual behaviors and health outcomes in Japan. Compared to other high-income countries, levels of sexual inexperience and inactivity seem to be high in Japan.

Salaries, degrees, and babies: Trends in fertility by income and education among Japanese men and women born 1943–1975—Analysis of national surveys

Background

While fertility rates have decreased during the second half of the 20^th century in Japan, little is known regarding trends in the number of children that men and women have across birth cohorts and whether these differ by education and income.

Methods

We used data from four rounds of the National Fertility Survey (1992, 2005, 2010 and 2015) and included men and women aged 40–49 years (16728 men and 17628 women). By 5-year birth cohorts, we assessed the distribution of number of children (0, 1, 2 and 3 or more) and total fertility (the mean number of children) at completed fertility (age 45–49 or 40–44 years depending on birth cohort). We assessed trends in these fertility outcomes in men and women separately, and by education (no university education; university education) for men and women and by reported annual income (0 to <3 000 000 JPY; 3 000 000 to <6 000 000 JPY; ≥6 000 000 JPY) for men.

Results

When comparing those born in 1943–1948 with those born in 1971–1975, the proportion with no children had increased from 14.3 to 39.9% for men and from 11.6 to 27.6% for women. This increase coincided with a decrease in the proportions of individuals with 2 or more children. Total fertility had decreased from 1.92 to 1.17 among men and from 1.96 to 1.42 among women. For men, those with a university degree were more likely to have children than those without a university degree in all birth cohorts except 1943–1947. Men with higher income were more likely to have children across birth cohorts. While the proportion who had children had decreased in all income groups, the decrease was steeper among those in the lowest income group. Among women born 1956–1970, those with a university degree were less likely to have children than those without a university degree; this difference was no longer seen among those born 1971–1975. For both men and women, trends in having children and total fertility across birth cohorts did not differ by educational status.

Conclusions

The decline in the total fertility rate in Japan can be attributed to both an increasing proportion of the population who have no children and a lower number of children among those who have children. Men with lower education and income were less likely to have children and the disparity in the number of children that men have by income had increased in more recent birth cohorts. Among women, higher education was associated with lower fertility, although this pattern was no longer observed among those born in 1971–1975.

Trends in lung cancer incidence by gender, histological type and stage at diagnosis in Japan, 1993-2015: A multiple imputation approach

Continued decrease in smoking prevalence and increasing use of sensitive diagnostic procedures necessitate updated monitoring of trends in lung cancer incidence in Japan. We analyzed histology- and stage-specific trends in 1993-2015 using data from 62,870 diagnosed cases from the Monitoring of Cancer Incidence in Japan project. After applying a multiple imputation approach to impute missing/unknown values of stage and histology, we estimated age-standardized incidence rates and applied joinpoint regression analyses. We observed long-term growth trends in adenocarcinoma (ADC) and localized cancer among both genders, long-term declining trends among men and leveling-off trends among women in small-cell carcinoma (SMC) and squamous cell carcinoma (SQC). Stratifying by gender, we observed an increase in localized ADC with average annual percentage changes (AAPC) of 4.5 (95% confidence interval: 3.9 to 5.0) and 5.7 (5.0 to 6.4), a decrease in regional ADC with AAPC of -1.5 (-2.5 to -0.6) and -2.3 (-4.6 to 0.0), but an increase in distant ADC with AAPC of 1.5 (1.1 to 1.9) and 1.6 (0.9 to 2.3) among males and females, respectively. Additionally, increasing trends in female-to-male incidence rate ratios were observed in localized ADC with significantly above one in the most recent diagnosis period. Our results revealed evidence for a partial shift from advanced to early cancer stage, which may suggest the modest effectiveness of nationwide organized screening programs. The observed increasing localized and distant ADC may be linked to improved diagnostic procedures, especially for metastasis detection. Further investigation is needed for more accurate quantification of these factors.

Antecedents of the Attitudes Toward Singlehood Among Young Adults in Malaysia, Japan, and India

With both theories and empirical studies supporting the benefits of having a romantic relationship, there remains an increasing tendency of staying single being documented globally. It is thus important to understand the antecedent factors of such voluntary single movement. Guided by the Investment Model of Commitment (IMC) process, the roles of subjective socioeconomic status (SSES), relational mobility, and desirability of control in attitudes toward singlehood were investigated. A total of 1,108 undergraduate students from Malaysia (n=444), Japan (n=316), and India (n=348) answered an online survey consisting of the Attitudes toward Singlehood Scale, MacArthur Scale of SSES, Relational Mobility Scale, Desirability of Control Scale, Mini-Social Phobia Inventory, and Single Item Narcissism Scale. Hierarchical multiple regression analysis showed a persistent positive relationship between desirability of control, but not socioeconomic status and relational mobility, with attitudes toward singlehood, even after statistically excluding the effects of social anxiety and narcissism. A similar pattern was also observed among those who were currently single. Moreover, an interaction effect of socioeconomic status and relational mobility was found in further exploratory analysis. The results highlight that retaining the autonomy and flexibility of managing one's own life and financial concern are the key reasons young adults prefer staying single to engaging in a romantic relationship. Implications and recommendations for future research are also presented in this study.